For the sake of clarity, a North/South (e.g., elevation) and East/West (e.g., lateral) orientation reference system is used in this document to describe dimensions and directions in a plane defined by the keyboard layout (e.g., a virtual keyboard and/or an overlay keyboard). The northern most alpha row of a QWERTY keyboard is designated Row 1 and at least contains the letter keys “Q”, “W”, “E”, “R”, “T”, “Y”, “U”, “I”, “O”, “P.” Row 2, the next row south of row 1, is also referred to as the “home row” and contains at least the letters “A”, “S”, “D”, “F”, “G”, “H”, “J”, “K” and “L.” The touch typist places eight fingers on specific keys in the home row, rests them there when not typing, and returns to them while typing in order to reorient their fingers. These keys are referred to as the “home row rest keys.” On a standard QWERTY keyboard, these are the “ASDF” keys for the four left fingers and the “JKL”; keys for the right four fingers. Row 3, the next row south of Row 2, contains at least the letters “Z”, “X”, “C”, “V”, “B”, “N”, and “M.” Row 4, the next row south of Row 3, is also referred to as the “space-bar row.” The directions “vertical”, “straight up”, “straight down”, or “normal” are used synonymously and interchangeably to describe trajectories essentially transverse (e.g., such as perpendicular) to a plane defined by the entire keyboard layout, or in the case of digital tablets, approximately perpendicular to the glass touch-screen. Note that this is simply a labeling mechanism—the present technology is not dependent on the keyboard layout of the underlying virtual keyboard. As such, the present technology can be applied to other configurations, such as, AZERTY, Dvorak, numeric, split keyboard, or any other keyboard layout used for touch typing with similar functionality explained below.
Keyboard overlays, such as those described in U.S. Pat. No. 8,206,047, which is commonly owned with the present application and incorporate by reference herein in its entirety (attached as Appendix A), enhance touch typing on touch screen devices, such as the iPad® tablet computer manufactured by Apple, Inc. A keyboard overlay is designed to go on top of the virtual keyboard on a touch screen device, and adds physical elements that provide tactile feedback to determine the location of the keys. A keyboard overlay also allows users to rest their fingers on the home row without accidentally triggering the virtual keys of a touch screen. The keyboard overlay is composed of multiple key structures, each of which is oriented over a corresponding virtual key on the underlying virtual keyboard. The overlay key structures have mechanical geometries that emulate the performance and tactile characteristics of mechanical key switches of conventional computer keyboards, and provide new performance and tactile characteristics that have no equivalent mechanical keyboard counterpart.
Several embodiments of keyboard overlays disclosed in U.S. Pat. No. 8,206,047 provide a solution to a number of issues that arise when touch-typing on the virtual keyboard of a touch screen device. For example, without a keyboard overlay as described in U.S. Pat. No. 8,206,047, touch typing is difficult because of the following issues:
1. Typists cannot rest their fingers on the home row of the virtual keyboard displayed on the touch screen since this would immediately trigger multiple unwanted key actuations.
2. There is no mechanism for decelerating the typist's fingers before they impact the touch screen. Given the ballistic nature of high speed touch typing, typist's fingers strike the hard touch screen at a high rate of speed with every key stroke. This can result in significant discomfort for the typist and increases the likelihood of repetitive stress injuries over time.
3. It is difficult for touch typists to reliably ascertain that they have correctly actuated a key when typing rapidly on these devices, since there is no subliminal tactile cue prior to actuation. The only tactile cue the user receives is from impact with the touch screen. This causes a significant decrease in typing speed and increases error rates.
4. There is no spring-back when the typist reverses their finger after completing a stroke. This results in slower typing speeds and less comfort while typing.
5. There are no tactile reference points for detecting the location of keys on the virtual keyboard. Thus, it is very easy for a touch typist's fingers to inadvertently drift off the key locations over time during typing. In order to compensate, typists must look down at the keyboard at all times. This eliminates one of the major benefits of touch typing—allowing the typist to focus their attention on something other than the keyboard while typing.
Keyboard overlays, such as several embodiments described in U.S. Pat. No. 8,206,047, are designed to work in cooperation with the software used to implement the virtual keyboard of a touch screen device to enable effective touch-typing on a touch screen device. For example, the characteristics of virtual keyboard software in modern touch screen devices are described and shown in U.S. Pat. Nos. 7,479,949 7,602,378, 7,614,008, 7,844,914, 7,602,378, 7,614,008, 7,812,828 and 7,941,760.
In operation, several relevant features of virtual keyboard software from a keyboard overlay perspective are as follows:
1. The virtual keyboard software extends the actual touch detection area of a key into the visual border (e.g., grey area) that visually separates the keys. Therefore, all locations on the virtual keyboard will register a key press when touched. The hit detection boundary between two keys is equidistant between the visible borders of the keys.
2. When a finger strike overlaps two or more key hit detection boundaries, virtual keyboard software determines the area (e.g., oval shape) of the multiple touch screen points actuated by the pad of the user's finger. The area of the finger strike within each virtual key's hit detection boundary is computed, and the key press is registered to the virtual key that has the largest area.
Several embodiments of the keyboard overlays described in U.S. Pat. No. 8,206,047 take advantage of these software features by not blocking any significant part of the finger oval from the underlying virtual keyboard.
Nonetheless, the lateral key pitch (East/West distance from the center of one key to the center of the adjacent key) of the underlying virtual keyboard is one factor in the effectiveness of a keyboard overlay for touch typing, and the importance of lateral key pitch complicates touch typing as touch screen devices get smaller and the key pitch shrinks.
A full size mechanical keyboard has a lateral key pitch of 19-19.5 mm. In contrast, the Apple iPad® has a 9.7 inch (246.4 mm) diagonal touch screen size that allows for a virtual keyboard with 18 mm lateral key pitch. Even though this is smaller than the key pitch of a full-size mechanical keyboard, sophisticated virtual keyboard software and an effective keyboard overlay can make touch typing on a virtual keyboard of this size work well. However, new tablet computers with even smaller virtual keyboards are now in the market.
For example, the Apple iPad mini° has a 7.9 inch (200.7 mm) touch screen size with a key pitch of only 14 mm. Touch typing becomes extremely difficult for many people with a lateral key pitch of only 14 mm. Many users simply don't have enough physical room to place all their fingers on the home row and still move their fingers in an unrestricted manner while typing on this device.